The present invention is related to cutting tools and more particularly to finish reamers.
In a wide variety of manufacturing and repair or reconditioning processes, it is necessary to accurately cut a hole or bore to a predetermined inner diameter. For example, such a cutting operation is performed in some of the various methods, which have heretofore been developed, for rebuilding of internal combustion engine valve guides. After extensive use, the valve guides of an internal combustion engine will wear, presenting excessive clearance between the valve guide and the valve stem. This excessive clearance may have an adverse effect on valve train operation and also increases undesirable emissions from the internal combustion engine.
The various methods heretofore proposed have included lining or relining of the worn valve guides with generally cylindrical inserts. In a typical rebuilding process, a worn valve guide is bored out to receive the insert which is press fit or forced into the bored out, valve guide passageway. The insert is finish reamed, so that the internal diameter is accurately cut and dimensioned with respect to the stem of the valve, which reciprocates within the rebuilt valve guide.
Inserts of various materials, such as cast iron, thin wall, silicon bronze-aluminum, manganese bronze, phosphor bronze, and the like, have been employed in such rebuilding methods. Cast iron inserts present certain inherent problems primarily related to cost, rate of wear, and heat transfer characteristics. In order to overcome these problems, different forms of bronze inserts have been developed. Notably, the bronze-based materials are harder than cast iron. However, the bronze-based inserts provide increased wear characteristics and heat transfer properties. Examples of inserts may be found in U.S. Pat. Nos. 3,828,415 entitled Method and Apparatus for Rebuilding Valve Guides, issued Aug. 13, 1974, to James A. Kammeraad et al., 4,103,662 entitled Insert for Rebuilding Valve Guides, issued Aug. 1, 1978, to James A. Kammeraad, and 5,249,555 entitled Valve Guide Insert, issued on Oct. 5, 1993, to James A. Kammeraad et al.
One of the inserts disclosed in U.S. Pat. No. 3,828,415 is a thin wall tubular member stamped from a blank of phosphor bronze and progressively formed into a tubular shape leaving a longitudinal slit. The insert is forced into a reamed valve guide by means of an adapter. The outer diameter of the insert is greater than the reamed valve guide, so that the insert is radially compressed when it is forced into the reamed valve guide. The insert is then trimmed, so that it is flush with the valve guide. The inner surface of the insert may then be knurled to flow the metal and seal off the passage through the slit. Finally, the valve guide is finish reamed to a predetermined diameter as required for the particular size of valve stem. The tubular insert has a wall thickness in the range of 10 to 25 thousandths of an inch and is preferably in the range of 15 to 20 thousandths of an inch. Another type of insert is disclosed in U.S. Pat. No. 4,103,662. It includes an inner sleeve or tube of spring-tempered phosphor bronze and an outer carrier sleeve or tube of steel or aluminum. The separate formation of the inner and outer sleeves allows precise control of wall thicknesses, diameters, and concentricities. Yet another type of insert is shown in U.S. Pat. No. 5,249,555. These inserts are made from phosphor bronze, but include thin walls having and tapered ends to facilitate insertion.
With each type of valve insert disclosed in the aforementioned patents, the finish-reaming step is typically performed with a high-speed reamer. Reamers are fabricated in a plurality of graduated standard diameter sizes to accommodate the different sizes of valve guides. The reamers each include a plurality of flutes, which define cutting blades. The flutes may be straight or spiral cut. Typically, a spiral flute reamer is used, since it provides a better finish and a smoother cutting of the insert passageway than a straight cut reamer.
Conventional reamer blades each include a rake face, a cutting edge, a land having constant-width, a margin and a relief, and a trailing portion. The land may be circular or convex and is typically relieved to avoid interference and rubbing with the work piece. Such reamers may be manufactured from high-speed steel, and a fluting cutter is employed to cut the flutes into the reamer blank. Further, the reamer portion may be back tapered to prevent binding of the reamer within the bore, which is being enlarged and finished. Examples of prior reamers may be found in U.S. Pat. Nos. 2,940,342 entitled Reamers, issued Jun. 14, 1969, to Lavallee, and 4,231,693 entitled Reamer with Radial Relief, issued Nov. 4, 1980, to James A. Kammeraad.
The finish reamers available prior to the reamers shown in U.S. Pat. No. 4,231,693 that were employed to finish the passageways of phosphor bronze valve inserts suffered from various problems primarily related to wearability. These prior reamers, after several reaming operations, were no longer able to hold their size. Continued use of the tool for additional reaming operations resulted in unacceptable dimensioning and finishing of the phosphor bronze valve guide insert.
The reamer shown in U.S. Pat. No. 4,231,693 has been highly successful, but further improvement is desired in terms of further extended tool life, further improved heat dissipation, and an improved configuration having less tendency to chatter, scuff, or drag on a finished surface, yet that maintains the effectiveness of the finishing section of the reamer. Nonetheless, the reamer itself must be readily manufacturable.
Therefore, an improved reamer is desired solving the aforementioned problems and having the aforementioned advantages.